The present invention relates to a new polymer which is extremely useful as a functional polymeric material such as light-sensitive and radiation-sensitive materials. More particularly, it relates to an alkali-soluble siloxane polymer in which more than 40% of the siloxane skeleton is composed of the unit represented by the formula (1); an alkali-soluble silmethylene polymer composed of the constitutional unit represented by the formula (2); and an alkali-soluble polyorganosilsesquioxane polymer represented by the formula (3). ##STR1## (where R.sub.1 is hydrogen or a monovalent organic group other than aromatic groups; R.sub.2 and R.sub.3 are each hydrogen, chlorine, or a monovalent organic group; l is an integer of 1 to 6; and k is 1 or 2.) ##STR2## (where R.sub.1, R.sub.2, and R.sub.3 are each a monovalent organic group; R.sub.4 is an alkyl group; l is 1 or 2; the OH groups and OR.sub.4 groups are at arbitrary positions on the benzene ring, m and n are positive integers and m+n is 2 to 200 and n/(m+n) is greater than 0.4.) ##STR3## (where R.sub.1 and R.sub.2 are the same or different organic groups; and n is a degree of polymerization.)
Electronic parts such as semiconductor devices and integrated circuits are produced by means of microetching with light or radiation. Etching requires a resist, and the resist of alkali-development type is predominant because of its high resolution. It contains as a basic polymer an alkali-soluble polymer such as phenolic resin and polyvinyl phenol. For example, a composition of phenol novolak resin and o-quinonediazide forms a positive photoresist, and a composition of polyvinyl phenol and bisazide forms a negative photoresist.
After patterning of the resist layer, the exposed substrate undergoes etching. In view of the trend to ever smaller circuit patterns of semiconductor devices, wet etching is being replaced by dry etching. Thus, a resist material is required to withstand dry etching. In the case where the substrate is an organic material, etching is carried out by an oxygen plasma. The conventional resist material is poor in resistance to oxygen plasmas, and there is a demand for the improvement in this regard.
In the meantime, the resist of alkali-development type is described in "Kodak Microelectronics Seminor Proceedings, 116 (1976), by J. C. Strieter.